The present invention relates to a method of manufacturing a semiconductor device and the semiconductor device. For example, the invention can be preferably applied to a semiconductor device using a nitride semiconductor.
GaN-based nitride semiconductor is expected to be used for a transistor in applications of high withstand voltage, high output, and high frequency because of its wide bandgap and high electron mobility compared with Si or GaAs, and has been actively developed in recent years. Among such transistors, a transistor having normally-off characteristics is useful, and a structure is earnestly investigated so that the transistor has the normally-off characteristics.
For example, Japanese Patent No. 5684574 discloses a semiconductor device including an under layer, an electron supply layer, a two-dimensional electron gas cancel layer, a first insulating film, and a gate electrode.
K. Kita and A. Toriumi “Origin of electric dipoles formed at high-k/SiO2 interface,” Applied Physics Letters vol. 94, 132902 (2009) describes a MOS device having a so-called high-k metal structure, in which a film stack including Al2O3 stacked on SiO2 is used as a gate insulating film to increase a threshold voltage.